Technical Description This four-year, field- and lab-intensive work extends the paleo-North Atlantic Oscillation (NAO) record to 2000 years BP, building on existing paleolimnological datasets of pollen, organic and inorganic chemistry, mineral magnetism and particle-size that show strong qualitative linkages with NAO activity on Iceland. It develops new quantitative linkages with the NAO from these same proxies in northwest Iceland lake, soil and stream deposits of the last 2000 years, using calibration datasets of watershed soil and lake sediments derived from current depositional environments. It identifies the specific environmental mechanisms responsible for creating distinct, 80-100 year cycles in the mineral deposits of Icelandic lakes and tests these hypotheses: 1. periods of intensified storminess and precipitation on Iceland, such as occur when the NAO index is high and positive, consistently and predictably mobilize minerals from watershed soil reserves and alter lake water characteristics to form distinctive lake sediment deposits, and 2. watershed disturbances related to human occupation and land-use increase the amplitude and/or recurrence interval of the decadal cycle, and 3. conservation protection of the lakes' watersheds in the last 30 years has resulted in a trend towards that of a pre-occupation state, as documented in the lake sediment geochemistry.
Broader impact The North Atlantic Oscillation (NAO) is part of a global-scale circulation pattern that dominates Northern Hemisphere atmospheric conditions. It is linked to patterns of drought, flooding and severe weather in North America, Europe and the Middle-East. Prior work has shown that the NAO undergoes regular cycles that disturb watershed soils and alter nutrient inflows to lakes and rivers, at least on Iceland. This works uses that lake effect to "see" into the past 2000 years and identify when the NAO was most active. Because human occupation of Iceland began just over 1000 years ago, and this project produces records of change covering the last 2000 years, it offers a unique look at the human role in magnifying the impacts of NAO-related climate changes on fragile landscapes, such as occur in Iceland and in many other previously glaciated regions. By assessing the response of watersheds to repeated climate disturbances, like the NAO, before and after human land use and before and after conservation management, this work provides insight on the usefulness of conservation efforts in mitigating human aspects of climate change. This project also provides much needed research, education, field and laboratory training opportunities for undergraduate and graduate students at institutions with relatively limited research opportunities (Plymouth State University and Salem State College), providing access and engagement with three tier-one, research institutions (U. Maine, U. Colorado and U. Minnesota). Students are involved at every level of the project and learn state-of-the-art interdisciplinary approaches typically practiced at research-oriented institutions. It creates opportunities for students to communicate complex ideas associated with research findings in oral and written publications. The five senior researchers involved in this project also receive training in state-of-the-art cross-disciplinary approaches and applications, which enhances their teaching and research capabilities. This work involves significant use of National Laboratory facilities at LacCore and Large Lakes Observatory and combines efforts of 3 New England campuses, leveraging existing facilities and human resources and building new regional capacity.
